Last updated: June 2026 · Reviewed June 2026 · Built by the InjectBuddy team
How many units is 500 IU of HCG twice weekly? the draw chart by vial and water volume
500 IU of HCG twice weekly is 10 units on a U-100 syringe when your vial sits at 5,000 IU/mL, and 50 units when it sits at 1,000 IU/mL — the exact mark depends entirely on how much bacteriostatic water you used to reconstitute. This guide explains the formula, works through eight examples for 5,000 and 10,000 IU vials, and answers the questions people ask most about drawing this dose.
Key takeaways
- IU is a dose; a syringe unit is a volume mark. 500 IU only becomes a unit number once you know the concentration.
- Shortcut for a U-100 syringe: units = (500 ÷ concentration in IU/mL) × 100.
- 500 IU twice weekly = 1,000 IU/week. A 5,000 IU vial holds ten doses; a 10,000 IU vial holds twenty.
- Never copy someone else's unit mark — match their water volume first or the dose will be wrong.
Skip the arithmetic: enter your vial strength, water volume and 500 IU dose into the HCG dosage calculator and read the unit mark straight off.
Why 500 IU has no single unit answer
"HCG 500 IU is how many units" has no fixed answer because international units measure biological activity, not volume. A syringe unit is a mark on the barrel that measures the liquid you draw. The bridge between them is concentration — the IU packed into each milliliter once the dry vial is mixed with water.
Two facts settle every conversion: the vial strength (commonly 5,000 IU or 10,000 IU) and the bacteriostatic water added during reconstitution. The same 500 IU can read as 10, 20, 25 or 50 units depending only on that water volume. This page assumes a U-100 insulin syringe, where 100 units fills 1 mL; if that scale is new, start with HCG IU to syringe units explained.
How this is calculated
The conversion is three short steps. Find the concentration the vial reached after you added water, divide your 500 IU dose by it to get a volume in mL, then turn the mL into syringe units.
- Concentration (IU/mL) = total vial IU ÷ water added (mL)
- Draw volume (mL) = 500 IU ÷ concentration
- Syringe units (U-100) = draw volume (mL) × 100
Collapsed into one line for a U-100 syringe: units = (500 ÷ concentration) × 100. With the dose fixed at 500 IU, only the concentration you created at reconstitution moves the unit number.
5,000 IU vial, 1 mL water → 5,000 ÷ 1 = 5,000 IU/mL. 500 ÷ 5,000 = 0.10 mL × 100 = 10 units.
5,000 IU vial, 2 mL water → 5,000 ÷ 2 = 2,500 IU/mL. 500 ÷ 2,500 = 0.20 mL × 100 = 20 units. Twice the water doubles the unit count for the identical dose.
500 IU units chart for a 5,000 IU vial
The 5,000 IU vial is a common size dispensed for HCG alongside testosterone therapy. Each row below is the same 500 IU dose; only the water volume changes, and with it the unit mark you draw.
| Water added | Concentration | Draw volume | Units (U-100) |
|---|---|---|---|
| 1 mL | 5,000 IU/mL | 0.10 mL | 10 units |
| 2 mL | 2,500 IU/mL | 0.20 mL | 20 units |
| 2.5 mL | 2,000 IU/mL | 0.25 mL | 25 units |
| 3 mL | 1,667 IU/mL | 0.30 mL | 30 units |
| 5 mL | 1,000 IU/mL | 0.50 mL | 50 units |
5,000 IU vial, 2.5 mL water → 5,000 ÷ 2.5 = 2,000 IU/mL. 500 ÷ 2,000 = 0.25 mL × 100 = 25 units — a quarter of the barrel, easy to read.
5,000 IU vial, 3 mL water → 5,000 ÷ 3 = 1,667 IU/mL. 500 ÷ 1,667 = 0.30 mL × 100 = 30 units. Non-round water volumes still resolve cleanly here.
More water means a weaker concentration and a larger, easier-to-read unit number for the same dose — the principle covered in why water amount changes syringe units.
500 IU units chart for a 10,000 IU vial
If your vial is 10,000 IU, the powder is twice as concentrated, so 500 IU lands at a smaller unit mark for any given water volume. To get the same draw as a 5,000 IU vial you simply add twice as much water.
| Water added | Concentration | Draw volume | Units (U-100) |
|---|---|---|---|
| 2 mL | 5,000 IU/mL | 0.10 mL | 10 units |
| 4 mL | 2,500 IU/mL | 0.20 mL | 20 units |
| 5 mL | 2,000 IU/mL | 0.25 mL | 25 units |
| 10 mL | 1,000 IU/mL | 0.50 mL | 50 units |
10,000 IU vial, 2 mL water → 10,000 ÷ 2 = 5,000 IU/mL. 500 ÷ 5,000 = 0.10 mL = 10 units — identical to a 5,000 IU vial with 1 mL, because both reach 5,000 IU/mL.
The unit mark follows the concentration, not the vial size. For a side-by-side of the two formats, see HCG 5,000 IU vs 10,000 IU vials.
What 500 IU twice weekly means for your week and your vial
500 IU twice weekly totals 1,000 IU per week. Splitting it into two injections keeps each dose small and easy to read; doses are usually spaced every three to four days, though the timing is set by your prescriber. Low-dose hCG like this is used to maintain intratesticular testosterone during testosterone therapy and to support spermatogenesis, which is why twice-weekly schedules are common in that setting.
The schedule also tells you how long a vial lasts: vial strength ÷ 500 IU gives the dose count, and that ÷ 2 gives the weeks of supply — subject to the post-mixing storage window on the label.
5,000 IU ÷ 500 IU per dose = 10 doses. At 2 doses/week: 10 ÷ 2 = 5 weeks of doses, if storage limits allow.
10,000 IU ÷ 500 IU per dose = 20 doses. At 2 doses/week: 20 ÷ 2 = 10 weeks of doses on paper — often longer than the refrigerated shelf life after mixing.
Reconstituted HCG has a limited refrigerated shelf life set on the label, so a vial holding ten weeks of doses on paper may need discarding first. See HCG storage and expiry, and always follow the discard date on your product.
Common mistakes when drawing 500 IU
The most frequent error is copying someone else's unit number. A person drawing 25 units for 500 IU mixed their vial differently from one drawing 10 units — the dose is identical, the concentration is not.
- Assuming a fixed unit number. 500 IU is 10 units at 5,000 IU/mL but 50 units at 1,000 IU/mL.
- Confusing vial strength with concentration. A 5,000 IU vial is not 5,000 IU/mL until you state the water volume. Strength is the total in the vial; concentration is the amount per mL after mixing.
- Forgetting to recompute after re-mixing. A new vial reconstituted with a different water volume gives a different unit mark for the same 500 IU.
Drawing 10 units from a vial reconstituted to 2,500 IU/mL gives 0.10 mL × 2,500 = 250 IU, not 500 IU — half the intended dose. Always recompute against your own concentration.
That the same unit mark can mean different doses is the point of why 10 units does not always mean the same dose. HCG dosing should be set and supervised by a prescribing clinician; this page is a measurement tool, not a dosing recommendation.
So, how many units is 500 IU of HCG twice weekly?
500 IU of HCG twice weekly is between 10 and 50 units on a U-100 insulin syringe, depending on the concentration you created when you reconstituted your vial. The formula is always the same: divide 500 by your concentration in IU/mL to get the volume in mL, then multiply by 100 to read the syringe units. A 5,000 IU vial mixed with 1 mL of bacteriostatic water gives 5,000 IU/mL, so each 500 IU dose is 10 units; mixed with 2.5 mL it gives 2,000 IU/mL and the same dose becomes 25 units. Use the HCG dosage calculator to enter your exact vial strength and water volume and get the unit mark instantly.
Frequently asked questions
How many units is 500 IU of HCG on an insulin syringe?
I have a 5,000 IU vial and added 1 mL of water. What do I draw for 500 IU?
Is 500 IU twice weekly the same as 1,000 IU once a week?
How long does a 5,000 IU vial last at 500 IU twice weekly?
Why does the same 500 IU dose give my friend a different unit number?
Sources
- Novarel (chorionic gonadotropin) for injection — prescribing information (5,000 and 10,000 USP unit vials with bacteriostatic water diluent). DailyMed, U.S. National Library of Medicine. DailyMed label.
- Coviello AD, Matsumoto AM, Bremner WJ, et al. Low-dose human chorionic gonadotropin maintains intratesticular testosterone in normal men with testosterone-induced gonadotropin suppression. J Clin Endocrinol Metab. 2005;90(5):2595-2602. PubMed 15713727.
- Hsieh TC, Pastuszak AW, Hwang K, Lipshultz LI. Concomitant intramuscular human chorionic gonadotropin preserves spermatogenesis in men undergoing testosterone replacement therapy. J Urol. 2013;189(2):647-650. PubMed 23260550.
- McBride JA, Carson CC, Coward RM. Diagnosis and management of testosterone deficiency. Asian J Androl. 2015;17(2):177-186. PMC4650468.
This guide is for general educational purposes only and does not constitute medical advice. HCG dose, schedule and reconstitution volume should be set by your prescribing clinician. Always follow the instructions and discard date on your specific product label.